If cared for properly,depending upon the leather type IMO the thicker stiff leathers which are smooth last the longest and look better over time where as the slouchy texured leathers tend to get more wear especially at the bottom where the panels front,side and rear panels get roll over and end up getting into contact with the ground or where ever it's placed.

IMO, a 35cm Birkin Bag if cared for with proper up keep and used every day in the following leather should last :

Vache Natural 40-50 years or more (typical corner wear and color changes expected)
Box Calf 40-50 years or more (typical corner wear expected)
Togo,Clemence,Barenia 30-35 years or more (corners and bottom seams and edges wear expected)
Fjord,Buffalo Gala,Water Buffalo 40 years possibly more (typical corner wear expected)
Courchevel,Epsom,Vache Leigee,Ardeenes 40 years possibly more ("" ^^^"" )
Swift,Veau Gulliver 30-35 years possibly more (corners and bottom seams and edges wear expected)
Chevre 30-35 years possibly more (depends on how stiff it is and if it has roll over or not)

Keeping in mind this is my guess for a bag used everyday over years upon years in the leathers given^^^ all will be expected to have corner wear ,color changes to the handles,rubs,hardware scratches,may need stitching repairs,etc...
Additionally smile marks and/or half circle cuts/scaring unnder the turn lock plate on those bag which have a swinging lock hung from the turn lock.

If cared for properly,depending upon the leather type IMO the thicker stiff leathers which are smooth last the longest and look better over time where as the slouchy texured leathers tend to get more wear especially at the bottom where the panels front,side and rear panels get roll over and end up getting into contact with the ground or where ever it's placed.

IMO, a 35cm Birkin Bag if cared for with proper up keep and used every day in the following leather should last :

Vache Natural 40-50 years or more (typical corner wear and color changes expected)
Box Calf 40-50 years or more (typical corner wear expected)
Togo,Clemence,Barenia 30-35 years or more (corners and bottom seams and edges wear expected)
Fjord,Buffalo Gala,Water Buffalo 40 years possibly more (typical corner wear expected)
Courchevel,Epsom,Vache Leigee,Ardeenes 40 years possibly more ("" ^^^"" )
Swift,Veau Gulliver 30-35 years possibly more (corners and bottom seams and edges wear expected)
Chevre 30-35 years possibly more (depends on how stiff it is and if it has roll over or not)

Keeping in mind this is my guess for a bag used everyday over years upon years in the leathers given^^^ all will be expected to have corner wear ,color changes to the handles,rubs,hardware scratches,may need stitching repairs,etc...
Additionally smile marks and/or half circle cuts/scaring unnder the turn lock plate on those bag which have a swinging lock hung from the turn lock.

Doc, you are the ultimate enabler!! Thank you for sharing all your knowledge!!

Folks appear to be asking more questions which I do no have the answers to... sorry.

I can say that ostrich wears very well and if cared for can be expected to do as well as most of the non exotic leathers however,quill bumps are often lost which is the main difference.

IMO reptile skins need special care to keep them nice enough for generations of use...

Snake skin being an exception to this. IMO any skin which comes from a reptile which sheds it's skin is delicate by nature and should not be considered to have any real longevity.
Someone asked about snake skin Birkins which to my knowledge are far from normal I have heard of only one having been made and not an Hermes typically used exotic skin.